Index: trunk/src/org/openstreetmap/josm/io/imagery/WMSImagery.java
===================================================================
--- trunk/src/org/openstreetmap/josm/io/imagery/WMSImagery.java	(revision 7220)
+++ trunk/src/org/openstreetmap/josm/io/imagery/WMSImagery.java	(revision 7221)
@@ -142,5 +142,5 @@
         URLConnection openConnection = Utils.openHttpConnection(getCapabilitiesUrl);
         StringBuilder ba = new StringBuilder();
-        
+
         try (
             InputStream inputStream = openConnection.getInputStream();
@@ -224,8 +224,8 @@
                 || format.startsWith("image/bmp") && ImageIO.getImageReadersBySuffix("bmp").hasNext();
     }
-    
+
     static boolean imageFormatHasTransparency(final String format) {
-        return format.startsWith("image/png") || format.startsWith("image/gif") 
-                || format.startsWith("image/svg") || format.startsWith("image/tiff");
+        return format != null && (format.startsWith("image/png") || format.startsWith("image/gif")
+                || format.startsWith("image/svg") || format.startsWith("image/tiff"));
     }